Convert README-included docs to proper crate-level documentation #2
Description
The current crate-level documentation that lives in lib.rs uses a really mediocre solution, it includes a duplicated README.md, which as duplicated due to cargo errors when trying to target a path in the crate's parent directory.
I suggest we rewrite the current workspace-level README.md into proper outer doc comments, which would let us get rid of the duplicate germterm/src/README.md hack.